The Nucleic Acids Core will be within the Nucleic Acids Laboratory at the Institute for Molecular Genetics at Baylor College of Medicine. The Core will provide oligonucleotide synthesis, sequencing of cloned DNA samples, and PCR amplification and sequencing of specific regions of HIV-1. In situ hybridization studies will also be performed. The activities will build upon instruments and expertise already available. Data management will take advantage of the computer network already in place and will use the existing programs and routines. Samples for sequencing will be prepared by the individual investigators using protocols supplied by the Core. The materials will then be analyzed and data made available within one week for standard sequencing and one month for PCR sequencing. Materials for in situ hybridization analysis will be loaded onto slides and probed with S-labelled probes.